Areas Of Auditory Cortex Research Articles

The auditory P2 is influenced by pitch changes but not pitch strength and consists of two separate subcomponents

Abstract The P2 component of the auditory evoked potential has previously been shown to depend on the acoustic stimulus properties and prior exposure to the materials. Here, we show that it is also affected by acoustic changes, as P2 amplitudes were strongly enhanced in response to voice pitch changes with a stepwise pattern compared to dynamic pitch changes typical for natural speech, and also reflected the magnitude of these pitch changes. Furthermore, it is demonstrated that neither the P2 nor any other component is affected by the harmonicity of the materials. Despite no prior exposure and a weaker pitch, artificially created inharmonic versions of the materials elicited similar activity throughout the auditory cortex. This suggests that so-called harmonic template neurons observed in animal studies are either absent or do not exist in sufficient number in the human auditory cortex to detect their activity extracranially. Crucially, morphology as well as scalp maps and source reconstructions of the EEG data showed that the P2 appears to consist of two separate subcomponents. While the “P2a” was localised to the auditory cortex, the subsequent “P2b” included generators spread across the auditory cortex and association areas. The two subcomponents thus likely reflect processing at different stages of the auditory pathway.

Effect of lidocaine on salicylate-induced tinnitus in guinea pigs: A focus on the auditory cortex.

This study aimed to investigate the effects of the intravenous administration of lidocaine in the auditory cortex after the systemic administration of salicylate. Healthy male albino Hartley guinea pigs were divided into two groups. The control group received only lidocaine, whereas the experimental group received lidocaine after checking for the effects of salicylate. Extracellular recordings of spikes in the primary auditory cortex and dorsocaudal areas in healthy albino Hartley guinea pigs were continuously documented (pre- and post-lidocaine, pre- and post-salicylate, and post-salicylate after adding lidocaine to post-salicylate). We recorded 160 single units in the primary auditory cortex from five guinea pigs and 155 single units in the dorsocaudal area from another five guinea pigs to confirm the effects of lidocaine on untreated animals. No significant change was detected in either the threshold or Q10dB value after lidocaine administration in the primary auditory cortex and dorsocaudal areas. Spontaneous firing activity significantly decreased after lidocaine administration in the primary auditory cortex and dorsocaudal areas. Next, we recorded 160 single units in the primary auditory cortex from five guinea pigs and 137 single units in the dorsocaudal area from another five guinea pigs to determine the effects of lidocaine on salicylate-treated animals. The threshold was significantly elevated after salicylate administration; however, no additional change was detected after adding lidocaine to the primary auditory cortex and dorsocaudal areas. Regarding the Q10dB value, lidocaine negated the significant changes induced by salicylate in the primary auditory cortex and dorsocaudal areas. Moreover, lidocaine negated the significant changes in spontaneous firing activities induced by salicylate in the primary auditory cortex and dorsocaudal areas. In conclusion, changes in the Q10dB value and spontaneous firing activities induced by salicylate administration are abolished by lidocaine administration, suggesting that these changes are related to the presence of tinnitus.

Potential role of Bcl2 in lipid metabolism and synaptic dysfunction of age-related hearing loss

Age-related hearing loss (ARHL) is a prevalent condition affecting millions of individuals globally. This study investigated the role of the cell survival regulator Bcl2 in ARHL through in vitro and in vivo experiments and metabolomics analysis. The results showed that the lack of Bcl2 in the auditory cortex affects lipid metabolism, resulting in reduced synaptic function and neurodegeneration. Immunohistochemical analysis demonstrated enrichment of Bcl2 in specific areas of the auditory cortex, including the secondary auditory cortex, dorsal and ventral areas, and primary somatosensory cortex. In ARHL rats, a significant decrease in Bcl2 expression was observed in these areas. RNAseq analysis showed that the downregulation of Bcl2 altered lipid metabolism pathways within the auditory pathway, which was further confirmed by metabolomics analysis. These results suggest that Bcl2 plays a crucial role in regulating lipid metabolism, synaptic function, and neurodegeneration in ARHL; thereby, it could be a potential therapeutic target. We also revealed that Bcl2 probably has a close connection with lipid peroxidation and reactive oxygen species (ROS) production occurring in cochlear hair cells and cortical neurons in ARHL. The study also identified changes in hair cells, spiral ganglion cells, and nerve fiber density as consequences of Bcl2 deficiency, which could potentially contribute to the inner ear nerve blockage and subsequent hearing loss. Therefore, targeting Bcl2 may be a promising potential therapeutic intervention for ARHL. These findings provide valuable insights into the molecular mechanisms underlying ARHL and may pave the way for novel treatment approaches for this prevalent age-related disorder.

The Development of Speaking and Singing in Infants May Play a Role in Genomics and Dementia in Humans.

The development of the central auditory system, including the auditory cortex and other areas involved in processing sound, is shaped by genetic and environmental factors, enabling infants to learn how to speak. Before explaining hearing in humans, a short overview of auditory dysfunction is provided. Environmental factors such as exposure to sound and language can impact the development and function of the auditory system sound processing, including discerning in speech perception, singing, and language processing. Infants can hear before birth, and sound exposure sculpts their developing auditory system structure and functions. Exposing infants to singing and speaking can support their auditory and language development. In aging humans, the hippocampus and auditory nuclear centers are affected by neurodegenerative diseases such as Alzheimer's, resulting in memory and auditory processing difficulties. As the disease progresses, overt auditory nuclear center damage occurs, leading to problems in processing auditory information. In conclusion, combined memory and auditory processing difficulties significantly impact people's ability to communicate and engage with their societal essence.

Is source-resolved magnetoencephalographic mismatch negativity a viable biomarker for early psychosis?

Mismatch negativity (MMN) is an auditory event-related response reflecting the pre-attentive detection of novel stimuli and is a biomarker of cortical dysfunction in schizophrenia (SZ). MMN to pitch (pMMN) and to duration (dMMN) deviant stimuli are impaired in chronic SZ, but it is less clear if MMN is reduced in first-episode SZ, with inconsistent findings in scalp-level EEG studies. Here, we investigated the neural generators of pMMN and dMMN with MEG recordings in 26 first-episode schizophrenia spectrum (FEsz) and 26 matched healthy controls (C). We projected MEG inverse solutions into precise functionally meaningful auditory cortex areas. MEG-derived MMN sources were in bilateral primary auditory cortex (A1) and belt areas. In A1, pMMN FEsz reduction showed a trend towards statistical significance (F(1,50) = 3.31; p = .07), and dMMN was reduced in FEsz (F(1,50) = 4.11; p = .04). Hypothesis-driven comparisons at each hemisphere revealed dMMN reduction in FEsz occurred in the left (t(56) = 2.23; p = .03; d = .61) but not right (t(56) = 1.02; p = .31; d = .28) hemisphere, with a moderate effect size. The added precision of MEG source solution with high-resolution MRI and parcellation of A1 may be requisite to detect the emerging pathophysiology and indicates a critical role for left hemisphere pathology at psychosis onset. However, the moderate effect size in left A1, albeit larger than reported in scalp MMN meta-analyses, casts doubt on the clinical utility of MMN for differential diagnosis, as a majority of patients will overlap with the healthy individual's distribution.

Bilateral widefield calcium imaging reveals circuit asymmetries and lateralized functional activation of the mouse auditory cortex

Coordinated functioning of the two cortical hemispheres is crucial for perception. The human auditory cortex (ACx) shows functional lateralization with the left hemisphere specialized for processing speech, whereas the right analyzes spectral content. In mice, virgin females demonstrate a left-hemisphere response bias to pup vocalizations that strengthens with motherhood. However, how this lateralized function is established is unclear. We developed a widefield imaging microscope to simultaneously image both hemispheres of mice to bilaterally monitor functional responses. We found that global ACx topography is symmetrical and stereotyped. In both male and virgin female mice, the secondary auditory cortex (A2) in the left hemisphere shows larger responses than right to high-frequency tones and adult vocalizations; however, only virgin female mice show a left-hemisphere bias in A2 in response to adult pain calls. These results indicate hemispheric bias with both sex-independent and -dependent aspects. Analyzing cross-hemispheric functional correlations showed that asymmetries exist in the strength of correlations between DM-AAF and A2-AAF, while other ACx areas showed smaller differences. We found that A2 showed lower cross-hemisphere correlation than other cortical areas, consistent with the lateralized functional activation of A2. Cross-hemispheric activity correlations are lower in deaf, otoferlin knockout (OTOF-/-) mice, indicating that the development of functional cross-hemispheric connections is experience dependent. Together, our results reveal that ACx is topographically symmetric at the macroscopic scale but that higher-order A2 shows sex-dependent and independent lateralized responses due to asymmetric intercortical functional connections. Moreover, our results suggest that sensory experience is required to establish functional cross-hemispheric connectivity.

On the evolution of polysensory superior temporal sulcus and middle temporal gyrus: A key component of the semantic system in the human brain.

The primary auditory cortex and other early auditory cortical areas lie on Heschl's gyrus within the Sylvian fissure. On the adjacent lateral surface of the superior temporal gyrus, the cortex processes higher order auditory information leading to auditory perception. On the ventral surface of the temporal lobe in the primate brain, there are areas that process higher order visual information leading to visual perception. These sensory-specific auditory and visual processing regions are separated by areas that integrate multisensory information within the deep superior temporal sulcus in both the macaque monkey and human brains. In the human brain, the multisensory integration cortex expands and forms the adjacent middle temporal gyrus. The expansion of this multisensory region in the language-dominant hemisphere of the human brain is critical for the emergence of semantic processing, namely, the processing of conceptual information that is not sensory specific but rather relies on multisensory integration.

Simultaneous fMRI and tDCS for Enhancing Training of Flight Tasks.

There is a gap in our understanding of how best to apply transcranial direct-current stimulation (tDCS) to enhance learning in complex, realistic, and multifocus tasks such as aviation. Our goal is to assess the effects of tDCS and feedback training on task performance, brain activity, and connectivity using functional magnetic resonance imaging (fMRI). Experienced glider pilots were recruited to perform a one-day, three-run flight-simulator task involving varying difficulty conditions and a secondary auditory task, mimicking real flight requirements. The stimulation group (versus sham) received 1.5 mA high-definition HD-tDCS to the right dorsolateral prefrontal cortex (DLPFC) for 30 min during the training. Whole-brain fMRI was collected before, during, and after stimulation. Active stimulation improved piloting performance both during and post-training, particularly in novice pilots. The fMRI revealed a number of tDCS-induced effects on brain activation, including an increase in the left cerebellum and bilateral basal ganglia for the most difficult conditions, an increase in DLPFC activation and connectivity to the cerebellum during stimulation, and an inhibition in the secondary task-related auditory cortex and Broca's area. Here, we show that stimulation increases activity and connectivity in flight-related brain areas, particularly in novices, and increases the brain's ability to focus on flying and ignore distractors. These findings can guide applied neurostimulation in real pilot training to enhance skill acquisition and can be applied widely in other complex perceptual-motor real-world tasks.

Neural signatures of second language proficiency in narrative processing.

Making sense of speech in a second language relies on multiple abilities. Differences in brain activity related to proficiency in language tasks have often been attributed to processing demands. However, during naturalistic narrative comprehension, listeners at different proficiency levels may form different representations of the same speech. We hypothesized that the intersubject synchronization of these representations could be used to measure second-language proficiency. Using a searchlight-shared response model, we found highly proficient participants showed synchronization in regions similar to those of native speakers, including in the default mode network and the lateral prefrontal cortex. In contrast, participants with low proficiency showed more synchronization in auditory cortex and word-level semantic processing areas in the temporal lobe. Moderate proficiency showed the greatest neural diversity, suggesting lower consistency in the source of this partial proficiency. Based on these synchronization differences, we were able to classify the proficiency level or predict behavioral performance on an independent English test in held-out participants, suggesting the identified neural systems represented proficiency-sensitive information that was generalizable to other individuals. These findings suggest higher second-language proficiency leads to more native-like neural processing of naturalistic language, including in systems beyond the cognitive control network or the core language network.

Mu-opioid receptor system modulates responses to vocal bonding and distress signals in humans.

Laughter is a contagious prosocial signal that conveys bonding motivation; adult crying conversely communicates desire for social proximity by signalling distress. Endogenous mu-opioid receptors (MORs) modulate sociability in humans and non-human primates. In this combined PET-fMRI study (n = 17), we tested whether central MOR tone is associated with regional brain responses to social signals of laughter and crying. MOR availability was measured with positron emission tomography (PET) using the high-affinity agonist radioligand [11C]carfentanil. Haemodynamic responses to social laughter and crying vocalizations were measured using functional magnetic resonance imaging (fMRI). Social laughter evoked activation in the auditory cortex, insula, cingulate cortex, amygdala, primary and secondary somatosensory cortex, and primary and secondary motor cortex; crying sounds led to more restricted activation in the auditory cortex and nearby areas. MOR availability was negatively correlated with the haemodynamic responses to social laughter in the primary and secondary somatosensory cortex, primary and secondary motor cortex, posterior insula, posterior cingulate cortex, precuneus, cuneus, temporal gyri and lingual gyrus. For crying-evoked activations, MOR availability was negatively correlated with medial and lateral prefrontal haemodynamic responses. Altogether our findings highlight the role of the MOR system in modulating acute brain responses to both positive and negative social signals. This article is part of the theme issue 'Cracking the laugh code: laughter through the lens of biology, psychology and neuroscience'.

Decreased BOLD signals elicited by 40-Hz auditory stimulation of the right primary auditory cortex in bipolar disorder: An fMRI study.

BackgroundA number studies have been conducted on abnormalities in the cortical circuitry of gamma oscillations, including deficit in auditory steady-state response (ASSR) to gamma-frequency (≧ 30-Hz) stimulation, in patients with bipolar disorder (BD). In the current study, we investigated neural responses during click stimulation by blood oxygen level-dependent (BOLD) signals. We focused on Broadman 41 and 42, the main sources of ASSR.Materials and methodsWe acquired BOLD responses elicited by click trains of 80-, 40-, 30- and 20-Hz frequencies from 25 patients with BD to 27 healthy controls (HC) with normal hearing between 22 and 59 years of age assessed via a standard general linear-model-based analysis. We extracted contrast values by identifying the primary auditory cortex and Brodmann areas 41 and 42 as regions of interest (ROI)s.ResultsBD group showed significantly decreased ASSR-BOLD signals in response to 40-Hz stimuli compared to the HC group in the right Brodmann areas 41 and 42. We found significant negative correlations between the BOLD change in the right Brodmann areas 41 and 42 and Structured Interview Guide for the Hamilton Depression Rating Scale (SIGH-D) scores, also the BOLD change in the right Brodmann areas 41 and 42 and the Positive and Negative Syndrome Scale (PANSS)-Negative scores.ConclusionThe observed decrease in BOLD signal patterns in the right primary auditory cortex during 40-Hz ASSR may be a potential biomarker option for bipolar disorder.

Kernel SVM Classifiers based on Fractal Analysis for Estimation of Hearing Loss

Hearing screening consists of analyzing the hearing capacity of an individual, regardless of age. It identifies serious hearing problems, degree, type and cause of the hearing loss and the needs of the person to propose a solution. Auditory evoked potentials (AEPs) which are detected on the EEG auditory cortex area are very small signals in response to a sound stimulus (or electric) from the inner ear to the primary auditory areas of the brain. AEPs are noninvasive methods used to detect hearing disorders and to estimate hearing thresholds level. In this paper, due to the nonlinear characteristics of EEG, Detrented Fluctuation Analysis (DFA) is used to characterize the irregularity or complexity of EEG signals by calculating the Fractal Dimension (FD) from the recorded AEP signals of the impaired hearing and the normal subjects. This is to estimate their hearing threshold. In order to classify both groups, hearing impaired and normal persons, support vector machine (SVM) is used. For comparably evaluating the performance of SVM classifier, three kernel functions: linear, radial basis function (RBF) and polynomial are employed to distinguish normal and the abnormal hearing subjects. Grid search technique is selected to estimate the optimal kernel parameters. Our results indicate that the RBF kernel SVM classifier is promising; it is able to obtain a high training as well as testing classification accuracy.

Functional ultrasound imaging of recent and remote memory recall in the associative fear neural network in mice

Emotional learning and memory are affected in numerous psychiatric disorders. At a systems level, however, the underlying neural circuitry is not well defined. Rodent fear conditioning (FC) provides a translational model to study the networks underlying associative memory retrieval. In the current study, functional connectivity among regions related to the cue associative fear network were investigated using functional ultrasound (fUS), a novel imaging technique with great potential for detecting neural activity through cerebral blood flow. Behavioral fear expression and fUS imaging were performed one and thirty-one days after FC to assess recent and remote memory recall. Cue-evoked increases in functional connectivity were detected throughout the amygdala, with the lateral (LA) and central (CeA) amygdalar nuclei emerging as major hubs of connectivity, although CeA connectivity was reduced during remote recall. Hippocampal and sensory cortical regions displayed heightened connectivity with the LA during remote recall, whereas interconnectivity between the primary auditory cortex and temporal association areas was reduced. Subregions of the prefrontal cortex exhibited variable changes, where prelimbic connectivity with the amygdala was refined while specific connections between the infralimbic cortex and amygdalar subregions emerged during remote memory retrieval, a signature of extinction memory. Moreover, freezing behavior positively correlated with functional connectivity between hubs of the associative fear network, suggesting that emotional response intensity reflected the strength of the cue-evoked functional network. Overall, our data provide evidence of the functionality of fUS imaging to investigate the neural dynamics of memory retrieval, applicable in the development of innovative treatments for affective disorders.

Cortical nicotinic enhancement of tone-evoked heightened activities and subcortical nicotinic enlargement of activated areas in mouse auditory cortex

Systemic nicotine administration regulates neuronal activities in mouse auditory cortex. How nicotine regulates the spread of the activities across auditory cortical areas is not well known. We investigate this using flavoprotein fluorescence imaging. 20 kHz amplitude-modulated (AM) tones increased the peak intensity of flavoprotein fluorescence in presumptive primary auditory cortex (A1). 5 kHz AM tones activated at least three cortical areas, which are presumably A1, anterior auditory field, and secondary auditory cortex. Nicotine enlarged tone-activated cortical areas and enhanced both 20 kHz and 5 kHz tone-evoked fluorescence intensities at their respective, optimal frequency peak sites and at non-optimal frequency peak sites in A1. The extent of this enhancement was greater at non-optimal frequency sites than at optimal frequency sites. A cortical injection of dihydro-β-erythroidine, an inhibitor of nicotinic acetylcholine receptors composed of α4 and β2-subunits (α4β2*-nAChRs), blocked the enhancement of fluorescence intensity at the peak sites but did not appear to block the enlargement of activated areas. These results suggest that nicotine exposure activates cortical α4β2*-nAChRs to enhance tone-evoked local neuronal activities at an optimal frequency site. The nicotine-induced enlargement of a tone-activated area may depend on the nicotinic enhancement of cortical inputs or other activities.

Evaluation of Structural Neural Connectivity Between the Primary Auditory Cortex and Cognition-Related Brain Areas Using Diffusion Tensor Tractography in 43 Normal Adults.

BackgroundLittle is known about the structural neural connectivity between the primary auditory cortex and cognition-related brain areas in the human brain. This study aimed to evaluate the structural neural connectivity between the primary auditory cortex and cognition-related brain areas in normal subjects, using diffusion tensor tractography (DTT).Material/MethodsForty-three healthy subjects with no prior history of audiological, neurological, physical, or psychiatric illnesses were recruited for this study. Diffusion tensor imaging data analysis was performed using the Oxford Centre for Functional Magnetic Resonance Imaging of Brain (FMRIB) Software Library. In each subject, a region of interest was set on the primary auditory cortex, including the subcortical white matter. We assessed the neural connectivity between the primary auditory cortex and cognition-related brain areas (the dorsolateral prefrontal cortex [DLPFC]; ventrolateral prefrontal cortex [VLPFC]; orbitofrontal cortex [OFC]; hippocampus; parahippocampal cortex; amygdala, anterior and posterior cingulate gyrus; and fornix).ResultsAccording to the results of DTT, the primary auditory cortex showed neural connectivity (over 50%) with the following areas: the threshold of 1 streamline – the VLPFC (94.2%), OFC (84.9%), fornix (80.2%), hippocampus (76.7%), parahippocampal cortex(74.4%) and DLPFC (58.1%); the threshold of 5 streamlines – the VLPFC (88.4%), OFC (81.4%), fornix (66.3%), hippocampus (55.8%), and parahippocampal cortex (53.5%); and the threshold of 15 streamlines – the VLPFC (82.6%), OFC (74.4%), and fornix (53.5%).ConclusionsIn normal human subjects, DTT showed that the primary auditory cortex had a high degree of neural connectivity with the prefrontal cortex, fornix, hippocampus, and parahippocampal cortex, which are brain areas associated with cognition and memory.

A genetic algorithm-based support vector machine model for detection of hearing thresholds

ABSTRACT Auditory evoked potentials (AEPs), which are detected on the EEG auditory cortex area, are very small signals in response to a sound stimulus (or electric) from the inner ear to the cerebral cortex. These signals are recorded from electrodes attached to the scalp and are used for measuring the bioelectric function of the auditory pathway. In order to characterise their dynamic behaviour and due to the complex behaviour of nonlinear dynamic properties of EEG signals, several nonlinear analyses have been performed. In this work, Detrented Fluctuation Analysis (DFA) is applied to estimate the Fractal Dimension (FD) from the recorded AEP signals of the normal and the impaired hearing subjects. This aims at detecting their hearing threshold level. With the aim of classifying both groups, the normal and hearing impaired subjects, a hybrid approach based on the Support Vector machines (SVM) and genetic algorithms (GA) is taken: GA is applied to simultaneously optimise both SVM kernel parameters and feature subset selection. Our results indicate that the hybrid GA-SVM is promising; it is able to determine well the SVM kernel parameters along with feature subset selection, which will result in a high classification accuracy.

The effect of systemic administration of salicylate on the auditory cortex of guinea pigs

To investigate the effect of systemic administration of salicylate as a tinnitus inducing drug in the auditory cortex of guinea pigs. Extracellular recording of spikes of the primary auditory cortex and dorsocaudal areas in healthy male albino Hartley guinea pigs was continuously performed (pre- and post-salicylate). We recorded 160 single units in the primary auditory cortex from five guinea pigs and 156 single units in the dorsocaudal area from another five guinea pigs. The threshold was significantly elevated after the administration of salicylate in both the primary auditory cortex and dorsocaudal areas. The Q10dB value was significantly increased in the primary auditory cortex, whereas it has significantly decreased in the dorsocaudal area. Spontaneous firing activity was significantly decreased in the primary auditory cortex, whereas it has significantly increased in the dorsocaudal area. Salicylate induces significant changes in single units of both stimulated and spontaneous activity in the auditory cortex of guinea pigs. The spontaneous activity changed differently depending on its cortical areas, which may be due to the neural elements that generate tinnitus.

The Influence of the Head Model Conductor on the Source Localization of Auditory Evoked Potentials.

The accuracy of EEG source analysis reconstruction improves when a realistic head volume conductor is modeled. In this study we investigated how the progressively more complex head representations influence the spatial localization of auditory-evoked potentials (AEPs). Fourteen young-adult participants with normal hearing performed the AEP task. Individualized head models were obtained from structural MRI and diffusion-weighted imaging scans collected in a separate session. AEPs were elicited by 1kHz and 4kHz tone bursts during a passive-listening tetanizing paradigm. We compared the amplitude of the N1 and P2 components before and after 4min of tetanic-stimulation with 1kHz sounds. Current density reconstruction values of both components were investigated in the primary auditory cortex and adjacent areas. Furthermore, we compared the signal topography and magnitude obtained with 10 different head models on the EEG forward solution. Starting from the simplest model (scalp, skull, brain), we investigated the influence of modeling the CSF, distinguishing between GM and WM conductors, and including anisotropic WM values. We localized the activity of AEPs within the primary auditory cortex, but not in adjacent areas. The inclusion of the CSF compartment had the strongest influence on the source reconstruction, whereas white matter anisotropy led to a smaller improvement. We conclude that individualized realistic head models provide the best solution for the forward solution when modeling the CSF conductor.

Auditory cortical micro-networks show differential connectivity during voice and speech processing in humans

The temporal voice areas (TVAs) in bilateral auditory cortex (AC) appear specialized for voice processing. Previous research assumed a uniform functional profile for the TVAs which are broadly spread along the bilateral AC. Alternatively, the TVAs might comprise separate AC nodes controlling differential neural functions for voice and speech decoding, organized as local micro-circuits. To investigate micro-circuits, we modeled the directional connectivity between TVA nodes during voice processing in humans while acquiring brain activity using neuroimaging. Results show several bilateral AC nodes for general voice decoding (speech and non-speech voices) and for speech decoding in particular. Furthermore, non-hierarchical and differential bilateral AC networks manifest distinct excitatory and inhibitory pathways for voice and speech processing. Finally, while voice and speech processing seem to have distinctive but integrated neural circuits in the left AC, the right AC reveals disintegrated neural circuits for both sounds. Altogether, we demonstrate a functional heterogeneity in the TVAs for voice decoding based on local micro-circuits.

The Motor Basis for Misophonia.

Misophonia is a common disorder characterized by the experience of strong negative emotions of anger and anxiety in response to certain everyday sounds, such as those generated by other people eating, drinking, and breathing. The commonplace nature of these “trigger” sounds makes misophonia a devastating disorder for sufferers and their families. How such innocuous sounds trigger this response is unknown. Since most trigger sounds are generated by orofacial movements (e.g., chewing) in others, we hypothesized that the mirror neuron system related to orofacial movements could underlie misophonia. We analyzed resting state fMRI (rs-fMRI) connectivity (N = 33, 16 females) and sound-evoked fMRI responses (N = 42, 29 females) in misophonia sufferers and controls. We demonstrate that, compared with controls, the misophonia group show no difference in auditory cortex responses to trigger sounds, but do show: (1) stronger rs-fMRI connectivity between both auditory and visual cortex and the ventral premotor cortex responsible for orofacial movements; (2) stronger functional connectivity between the auditory cortex and orofacial motor area during sound perception in general; and (3) stronger activation of the orofacial motor area, specifically, in response to trigger sounds. Our results support a model of misophonia based on “hyper-mirroring” of the orofacial actions of others with sounds being the “medium” via which action of others is excessively mirrored. Misophonia is therefore not an abreaction to sounds, per se, but a manifestation of activity in parts of the motor system involved in producing those sounds. This new framework to understand misophonia can explain behavioral and emotional responses and has important consequences for devising effective therapies.SIGNIFICANCE STATEMENT Conventionally, misophonia, literally “hatred of sounds” has been considered as a disorder of sound emotion processing, in which “simple” eating and chewing sounds produced by others cause negative emotional responses. Our data provide an alternative but complementary perspective on misophonia that emphasizes the action of the trigger-person rather than the sounds which are a byproduct of that action. Sounds, in this new perspective, are only a “medium” via which action of the triggering-person is mirrored onto the listener. This change in perspective has important consequences for devising therapies and treatment methods for misophonia. It suggests that, instead of focusing on sounds, which many existing therapies do, effective therapies should target the brain representation of movement.